PROJECT SUMMARY The 20th Phagocyte Gordon Conference (GRC) and associated Gordon Research Seminar (GRS) will be held June 1-7, 2019 at Waterville Valley, Waterville Valley, New Hampshire. Phagocytes are defined by their ability to ingest other cells/particles and include neutrophils, monocyte/macrophages and dendritic cells. These cells play a central role in innate and adaptive immunity. However, these cells are also critical for maintaining tissue homeostasis, and, when dysregulated, cause pathological changes that contribute to some of the prevalent diseases seen globally, including atherosclerosis and diabetes. The theme of the 2019 Phagocytes GRC is ?Phagocyte Functions Through Life: Development, Defense and Disease? and it will be a forum for in-depth discussions of the most recent discoveries in phagocyte biology. Featured topics will include macrophage influences on tissue development, cytokines and their generation, cell death mechanisms, phagocytosis, host- pathogen interactions, their functional and phenotypic plasticity in different tissue environments, and exciting advances in microbiome-phagocyte interactions and the impact of aging on phagocyte function. The role of phagocyte dysfunction on prevalent diseases will also be discussed in the meeting. The translational value and the development of new therapies for phagocyte-related diseases will also be addressed. The conference draws from a world-wide group of scientists with backgrounds in cell biology, molecular genetics, microbiology, immunology, bioengineering, and clinical medicine. The meeting is an important venue for disseminating information and facilitating communication between investigators studying different facets of phagocyte function and provides a networking forum for trainees and young investigators. The average attendance is 148 attendees which has been deemed ?just the right number?. In 2017, 52% of the attendees and 49% of the speakers were women and more than 50% of attendees were graduate students or postdoctoral fellows; ~25% of the attendees had speaking opportunities. The program planned for the 2019 GRC includes nine sessions, chaired by discussion leaders who are experts in the field, where 25 invited speakers will present their latest and most exciting unpublished findings. In keeping with tradition, 12 junior scientists will be selected to present short talks based on their submitted abstracts and another 16 to give a brief preview of their poster. In addition to oral presentations, we expect at least 100 posters to be displayed at the meeting. To further promote the participation and professional development of students and postdoctoral fellows, the 2019 Conference will incorporate a Gordon Graduate Research Seminar (GRS) immediately prior to the start of the GRC (June 1-2) that is organized by trainees. This multifaceted program will provide opportunities for participation of scientists at all levels and promote the participation of junior investigators, postdoctoral trainees and new investigators to the field. Based on its? history, the Phagocytes GRC and GRS meetings will promote information exchange and collaborations that will drive the discovery of novel therapeutics.